1. Field of the Invention
The invention relates to automatic test equipment and more specifically to pre-test compensation for power applied by automatic test equipment to a device under test.
2. Description of the Related Art
Production testing of integrated circuits uses generic automatic test equipment (ATE) and a special-purpose adapter board to connect an arbitrary integrated circuit device under test (DUT) to a standard ATE interface. The typical adapter board is a printed circuit board (PCB) that is connected to the ATE and contains a socket to removably insert the DUT.
During testing, and particularly during high performance testing, there is often a voltage drop in power supplied to the DUT across the connection between the DUT and the socket. This voltage drop is different for each DUT insertion because of changes in connection resistance between the socket and the DUT. Additionally, this voltage drop is not representative of a voltage drop observed during field use of the device where the device may be connected via a permanently attachable socket with lower contact resistance.
The voltage drop across the socket may reduce the power at internal busses inside the DUT and lead to unreliable tests. Therefore, the test equipment may need to increase the voltage supplied to power the DUT to compensate for the voltage drop across the socket and produce reliable tests.
Because the voltage drop across the socket is different for each DUT insertion, a predetermined voltage increase may not compensate for the voltage drop. Rather, the test equipment may need to supply a unique voltage increase with each DUT insertion to compensate for the reduced voltage at internal busses inside the DUT.
U.S. Published App. No. 2004/0051551 proposes one solution to this problem, but the proposed solution requires a change to the internal circuitry of a DUT. These solutions require adding an additional voltage sensing connection terminal to the DUT for monitoring a voltage at the internal bus. These solutions involve adjusting the power supplied to the DUT until the voltage monitored at the sensing connection terminal is equal to a target voltage. These existing solutions have the problem of requiring changing the design of the DUT, which can be expensive and have unintended consequences on actual in-field usage of the DUT.
There exists a need, therefore, for providing reliable tests using test equipment by compensating for reduced voltage at an internal bus inside a DUT that preferably does not change the internal circuitry of the DUT.